Smog from burning coal cuts roughly three years on average off the lives of people in northern China compared with their southern counterparts, a new study suggests.

The report, based on air quality data in 154 cities from 1981 to 2012, found pollution levels were 46 per cent higher north of the Huai River, a dividing line between northern and southern China.

The study by researchers in China, Israel and the United States was published this week in the Proceedings of the National Academy of Sciences.

The researchers said poor air quality in the north meant people lost an average of 3.1 years of life compared to residents in the south due to the higher prevalence of illnesses such as lung cancer and stroke.

“The higher mortality rates are evident throughout the life cycle,” said Michael Greenstone, an energy and environment expert at the University of Chicago, who co-authored the study.

“They are not just among the young and the old, but we see them also among middle-aged people. It [air pollution] is affecting everyone.”

Coal-fired boilers have in the past been more widely used in colder northern China, partly due to government policies that provided free coal to households.

Northern China suffers from heavier smog, especially in the autumn and winter, when more coal is burned for heating.

Rising public discontent about the hazardous levels of smog has prompted the government to embark on an anti-air pollution campaign that has seen households forced to replace coal-fired heaters with electric or gas-fired units.

Such efforts are working, according to Greenstone.

A similar study in 2013, which he also co-authored, found the difference in life expectancy between the north and south was 5½ years.

However, the government admitted last month it was still under pressure to meet targets to significantly cut levels of PM2.5 – the small particles in air pollution most harmful to health.

Widespread air pollution continues to cause premature deaths across the country, especially in industrial regions, according to an air quality-life index compiled by researchers at the University of Chicago’s Energy Policy Institute.

The average Chinese person could live 3½ years longer if PM2.5 concentrations could be kept below standard levels set by the World Health Organisation, according to the institute. Beijing residents could enjoy an extra 6.4 years of life if the capital’s PM2.5 level met international standards, while people in the northern city of Harbin could live 6.9 more years, the institute said.

Many previous studies have highlighted the alarming health effects created by the country’s toxic smog.

A report by Nanjing University’s School of the Environment last year found smog was related to nearly one-third of deaths in the Beijing-Tianjin-Hebei region and the Yangtze River Delta and Pearl River Delta based on a study of mortality rates in 2013.

Another project by the US-based Health Effects Institute, published earlier this year found air pollution caused about 1.1 million premature deaths in China.